The present disclosure generally relates to turn signal assemblies for use in an automotive vehicle, and more particularly, to turn signal assemblies employing shape memory alloy actuated automatic cancellation mechanisms.
Most motor vehicles utilize a turn signal to provide a visible indicator to the driver and others external to the vehicle as to the intended direction of the vehicle. Initial activation of the turn signal is generally by hand movement of a turn signal assembly such as a turn signal stalk, button, switch, or the like. For example, on automotive vehicles the turn signal actuator is typically a turn signal stalk that is located on the left side of a steering column, movement of which generally corresponds to the intended direction of vehicle. Once the turn signal is activated by movement of the turn signal stalk, automatic cancellation is generally achieved via a ratchet or latch type mechanism that is initiated with a physical turning of the steering wheel. The implementation of ratchet and latch type mechanisms within the stalk is relatively complex, requires a relatively large amount of space within the stalk and/or steering column, and is not very robust for the various scenarios in which the turn signal is operated and cancelled.
Generally, the turn signals remain active until manually disabled by the occupant by physical movement of the stalk to the off position or when the steering wheel is turned a predetermined amount and returned. For example, when the steering wheel is turned past a designed-in arc angle in the direction of the intended turn, and subsequently returned, a mechanism is tripped to reset the turn signal to the off position. These pre-determined arc angles are designed by the motor vehicle manufacturer and are fixed angle points within the steering column. As such, multiple fixed angle points are generally utilized to provide a robust automatic cancellation mechanism.
Manually turning off the turn signal can generally be achieved in one of two ways. The first involves the operator physically moving the turn signal stalk back to its original off position. Secondly, the vehicle operator can manipulate the turn signal stalk to an intermediate position between the on and off positions so as to enable the turn signal. As long as the stalk is held in this position, the turn signal remains on. Removing the hand allows the turn signal stalk to return to its original off position. This mode is independent of the steering wheel position or movement and is generally implemented during a lane change, where the turning radius is minimal.
The problem with this art is that the automatic cancel feature generally responds to steering wheel rotation only, and/or employs a complex mechanism that is relatively bulky and expensive to produce. The fact that the current automatic cancel feature is not robust for all driving scenarios has been comprehended in some vehicles by the addition of a chime reminder, which is generally activated automatically based variously on miles or time driven. Accordingly, there remains a need in the art for less complex turn signal actuators that can be readily and easily programmed to account for the variety of scenarios for which automatic turn signal cancellation may be desired.